A network is a collection of devices, such as servers, work stations, telephones, PDAs, etc., that communicate with other either through hard-wires or wirelessly. In a switched network, a plurality of switch routers allows many nodes or hosts to be efficiently interconnected where blocks of data, referred to as packets or messages, can be transmitted from a source in the network to a host. A plurality of networks can be interconnected to form an internet.
Some networks employ a multicast protocol where a single message or packet can be sent to a particular IP address, and copies of the message are then delivered from IP address to a plurality of hosts that are part of a specified group, where a range of IP addresses identities the group. The hosts may join or be removed from a particular group at any time without talking to other member hosts in the group. One type of multicast routing protocol is known as protocol independent multicast (PIM), well known to those skilled in the art, that is able to build on any unicast routing protocol and allow a relatively small number of routers to receive network traffic for a particular group. PIM is typically separated into dense mode (DM) and sparse mode (SM). In PIM-DM most of the hosts in the system want to receive all of the multicast messages. In PIM-SM, generally only small groups of hosts want to receive any particular multicast message. In a PIM-SM network, the routers may use a bootstrap router (BSR) protocol, well known to those skilled in the art, to distribute rendezvous point information within the PIM-SM domain. The PIM-SM does the multicast routing, and may include unicast routes created by open shortest path first (OSPF) protocol, routing information protocol (RIP), static routes or other unicast routing protocols.
In PIM-SM, routers are able to join and leave multicast groups using PIM messages. A source, such as a server, may send a PIM multicast message to a group of hosts, such as a group of work stations. In order for the PIM-SM to work properly, it needs to use rendezvous points (RP). A rendezvous point is an IP address in a router that receives messages transmitted between a source and a group of hosts for a specified group range. The PIM assigns a rendezvous point at one of the switch routers for each group where the multicast message is sent for the group. Particularly, each multicast message transmitted from the source will be destined for a multicast group address that is included in a multicast group range that is represented by a single rendezvous point. Thus, for each defined group address in the network, a rendezvous point will be provided. In this type of network, each host is not interested in knowing the location of the source, but is only interested in knowing the rendezvous point for its group. Likewise, the source is only interested in sending the multicast message to the rendezvous point for the group from where it is disseminated to the group.
It is necessary that all of the routers in the network know which routers are the rendezvous point for which group. There are two known techniques for configuring rendezvous points in the switch routers for PIM-SM. One known technique is referred to as a static rendezvous point configuration. Static rendezvous point configuration requires the user to input rendezvous point commands using a router interface, such as a management console, into each router that identifies the rendezvous points for each group of work stations.
Alternatively, the BSR protocol can be used to configure the rendezvous points at the routers. In this technique, the user will input commands into one of the routers that identifies the groups, identifies which routers can be candidate rendezvous points and which routers can be a candidate BSR. The PIM defines a set of procedures by which all of the routers in the network can agree on which routers are rendezvous points for which group. The BSR will go through an election process based on predetermined BSR criteria to determine which of the routers will be an elected BSR. Once the BSR determines which router is the elected BSR router, the elected BSR will then determine which router is the rendezvous point for which groups.
There are disadvantages to both the static rendezvous point configuration and the BSR protocol rendezvous point configuration. Particularly, the static rendezvous point configuration requires each separate router to be manually configured with the rendezvous points for the groups, i.e., the rendezvous points are input to each router using PIM-SM commands. Thus, each switch router must be programmed with the static rendezvous point configuration for all of the routers, which is somewhat time consuming and cumbersome.
Configuring the rendezvous points in the switch routers using the BSR protocol requires a higher level of complexity that includes an election process, a BSR candidacy process, and an RP selection process that requires a significant period of time for the messages to be distributed to the switch routers to allow the switch router to learn which routers are the rendezvous points for which groups. Further, the BSR protocol rendezvous point configuration has the potential for mis-configuration and incomplete configuration. Also, the candidate rendezvous point information can change or time out during the BSR protocol rendezvous point configuration process.